Method and system for controlling cooling fans in a vehicle

ABSTRACT

A system and method is disclosed for cooling a control system in a vehicle. In one embodiment, the system comprises vehicle subsystems and a vehicle controller. The vehicle subsystems are configured to generate a plurality of subsystem temperature signals that are indicative of a measured temperature for each vehicle subsystem. The vehicle controller is configured to generate a desired fan speed signal for each vehicle subsystem in response to each subsystem temperature signal and to compare each desired fan speed signal to each other to determine a maximum desired fan speed signal. The vehicle controller controls the fan such that the fan reaches a fan speed that is equal to or greater than the maximum desired fan speed signal.

BACKGROUND

1. Technical Field

The embodiments of the invention described herein generally relate to cooling systems for use in a vehicle.

2. Background Art

In conventional vehicles, cooling fans are generally used to cool an engine. With Hybrid Electrical Vehicles (HEV) or fuel cell based vehicles, additional subsystems packaged in the engine compartment or elsewhere in the vehicle may benefit from being cooled to increase subsystem life span and to ensure optimal performance. Such subsystems may include various electrical based motors and power electronics associated with driving the motors.

Accordingly, it would be desirable to provide a system and method for controlling fan speed for a cooling fan to cool a number of subsystems in an HEV or fuel cell based vehicle.

SUMMARY

A system and method is disclosed for cooling a control system in a vehicle. In one embodiment, the system comprises vehicle subsystems and a vehicle controller.

The vehicle subsystems are configured to generate a plurality of subsystem temperature signals that are indicative of a measured temperature for each vehicle subsystem. The vehicle controller is configured to generate a desired fan speed signal for each vehicle subsystem in response to each subsystem temperature signal and to compare each desired fan speed signal to each other to determine a maximum desired fan speed signal. The vehicle controller controls the fan such that the fan reaches a speed that is equal to or greater than the maximum desired fan speed signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system in accordance to one embodiment of the present invention;

FIG. 2 illustrates a block diagram of various controllers in the system providing desired fan speed requests; and

FIG. 3 illustrates a flow diagram for controlling fan speed based on the desired fan speed requests.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 illustrates diagrammatically an overall vehicle system 100 in accordance to one embodiment of the present invention. The system 100 relates to electric vehicles, and more particularly, to Hybrid Electric Vehicles (HEV). FIG. 1, which generally illustrates one implementation of the system, is provided for exemplary purposes. The system 100 comprises a vehicle system controller (VSC) 102, a vehicle control system (or control system) 104 and a cooling system 106. The vehicle control system 104 is adapted to provide a plurality of temperature signals to the VSC 102. The VSC 102 is configured to control the cooling system 106 to cool the control system 104 in response to the temperature signals. The VSC 102 may be implemented as a stand-alone controller or may be integrated into one or more controllers in the control system 104.

The control system 104 generally comprises a number of subsystems. Such subsystems include an engine subsystem 107, a transmission subsystem 109, a starter-generator subsystem 111, a DC/DC converter 114 and a motor system 115. The engine subsystem 107 comprises an engine 108 and an engine controller 116. The engine 108 is generally referred to as a power generating device that may be used to power the vehicle by consuming fuel. The engine 108, for example, may be any internal combustion engine using a hydrocarbon based fuel, including but not limited to gasoline, diesel, hydrogen, methanol, natural gas, ethanol or other gas or liquid fueled internal combustion engine. Alternatively, the power generating device can be a fuel cell engine, such as a hydrogen-powered fuel cell engine. The engine controller 116 is adapted to control the operation of the engine 108.

A multiplexed data bus 118 is coupled to the VSC 102 and the engine controller 116 to facilitate data communication therebetween. In one example, the multiplexed data bus 118 may be implemented as a part of a high speed controller area network (CAN). In another example, the multiplexed data bus 118 may be implemented as a part of a local interconnect network (LIN). The particular type of multiplexed bus used in the system 100 may be one of various types to meet the desired criteria of a particular implementation.

The transmission subsystem 109 comprises a transmission 110 and a transmission controller 120. The transmission controller 120 controls the operation of the transmission 110. The transmission controller 120 may transmit/receive data signals to/from the VSC 102 over the multiplexed data bus 118.

The starter-generator subsystem 111 comprises a starter-generator 112 and a generator controller 122. The starter-generator 112 is coupled to the generator controller 122. The starter-generator 112 is adapted to start the engine 108. The generator controller 122 includes power electronic circuitry (not shown) and is adapted to control the operation of the starter-generator 112. The power electronic circuitry delivers power for driving the starter-generator 112. Such circuitry generally produces a large amount of heat while operating.

The starter-generator 112 may be implemented as a crank integrated starter-generator or as a belt-driven integrated starter-generator. The system 100 employs an engine stop-start function whereby the engine 108 is turned off via the starter-generator 112 in response to a command issued by the VSC 102. An example of where this may occur is when a determination is made by the motor controller 135 that the vehicle has come to a complete stop (e.g., vehicle comes to a halt in traffic). Under the control of the engine controller 116, the engine 108 is quickly started when it is necessary for the vehicle to move (e.g., vehicle coming out of halt in traffic). The generator controller 122 is adapted to transmit/receive data signal to/from the VSC 102 over the multiplexed data bus 118. The generator controller 122 may transmit data related to operating characteristics of the power circuitry and the starter-generator 112 over the multiplexed data bus 118 to the VSC 102.

The starter-generator 112 may be placed in series with the engine 108 and the transmission 110 and generate energy (electrical current) when the engine 108 is rotating. The generator controller 122 may provide high voltage over a high voltage bus 123. A battery 125 is coupled to the motor controller 135 via the high voltage bus 123. The battery 125 stores electrical current delivered from the DC/DC converter 114 and the motor controller 135. The DC/DC converter 114 is configured to step down high-voltage delivered over the high-voltage bus to produce low voltage. The DC/DC converter 114 provides the low voltage over a low voltage bus (not shown). The low voltage may be used by the engine controller 116, the transmission controller 120 and accessory devices (not shown) in the vehicle for power. Various examples of accessories that use low voltage to operate may include and are not limited to motor electronics coolant pump(s), engine cooling fan(s), battery cooling fan(s), brake vacuum pump, heated seats, heated mirrors, and heated window defrost. The DC/DC converter 114 is also adapted to transmit/receive data signals to/from the VSC 102 over the multiplexed data bus 118.

The engine 108 is generally placed in series with the transmission 110. A front torque output shaft 124 is coupled to the transmission 110. The transmission 110 is adapted to rotate the front axle mechanism 126 when the engine 108 is running. A front differential and axle assembly 126 is coupled to the front torque output shaft 124 and rotates wheels 128 at the front of the vehicle.

The motor system 115 comprises a motor 130 and a motor controller 135. The motor 130 is coupled to the motor controller 135. The motor controller 135 controls the operation of the motor 130. The motor controller 135 may transmit/receive data signals to/from the VSC 102 over the multiplexed data bus 118.

The system 100 further comprises a rear differential (not shown) and axle assembly 132. In one example, a rear torque output shaft 134 may be coupled between the electric motor 130, the rear differential and axle assembly 132. The axle assembly 132 drives rear wheels 136 in response to the motor 130 rotating the rear torque output shaft 134. The electric motor 130 may be coupled to the front torque output shaft 124 and/or the rear torque output shaft 134.

In general, the engine 108, the transmission 110, the starter-generator 112, the DC/DC converter 114, the generator controller 122 (e.g., power electronic circuitry) and the motor 130 may generate a significant amount of heat while operating. In some cases, it may be necessary to cool the subsystems to allow for optimal operation. The cooling system 106 generally comprises a first radiator 150, a first coolant loop 152, and a first pump 162. The first radiator 150 provides coolant through the first coolant loop 152. The pump 162 may be activated in response to control signals generated by the VSC 102 to move coolant through the first coolant loop 152. The pump 162 pumps coolant through the first coolant loop 152 to the engine 108 and the transmission 110 in the event the VSC 102 determines that the temperature is hotter than acceptable. The first coolant loop 152 may be configured to present coolant to any number of subsystems in the vehicle, and is not intended to be limited to providing coolant to only those subsystems mentioned.

The cooling system 106 comprises a second radiator 154, a second coolant loop 156 and a second pump 164. The second radiator 154 provides coolant through the second coolant loop 156. The pump 164 is activated in response to control signal by the VSC 102 to move coolant through the second coolant loop 156. The second pump 164 pumps coolant to the DC/DC converter 114, the motor 130, the motor controller 135, the starter-generator 112 and the generator controller 122 in the event the VSC 102 determines that the temperature is hotter than acceptable. The second coolant loop 156 may be configured to present coolant to any number of subsystems in the vehicle and is not intended to be limited to providing coolant to only those subsystems mentioned.

The cooling system 106 includes a cooling fan 160. The cooling fan 160 may be controlled by the VSC 102. The VSC 102 may control various speeds of the cooling fan 160 in response to the temperature signals generated from the control system 104. The control system 104 may generate temperature signals as multiplexed data messages that correspond to temperature characteristics for a particular subsystem in the control system 104. For example, the DC/DC converter 114, the engine controller 116, the transmission controller 120, the generator controller 122 and the motor controller 135 may each provide the temperature signal for a subsystem. The subsystems 107, 109, 111, 114, 115 and 122 may each be configured to provide the temperature signal based on actual measured temperatures of the particular component within the subsystem or a measured temperature of coolant within the first and second coolant loops 152 and 156, for a particular subsystem.

The VSC 102 may adjust the speed of the fan 160 and set the fan 160 to a maximum speed based on the temperature signals received by the subsystems 107, 109, 111, 114, 115 and 122. The VSC 102 may also activate the pumps 162, 164 to pump coolant through the first and second coolant loops 152, 156 based on the temperature signal received by the subsystems 107, 109, 111, 114, 115 and 122. Th VSC 102 may deactivate the pumps 162, 164 once the VSC 102 determines that the temperature signal from a particular subsystem that has the hottest temperature measurement is within an acceptable temperature range. The VSC 102 may not need to rely on comparing measured temperatures to calibratible thresholds or values in order to activate the pumps 162, 164 and to set the appropriate speed for the fan 160. The VSC 102 may control the speed of the fan 160 to cool the engine 108, the transmission 110, the starter-generator 112, the DC/DC converter 114, the generator controller 122 and the motor controller 135. If multiple cooling fans were used, the VSC 102 may independently control a particular fan speed for a particular fan based on the particular temperature signal for a particular subsystem in the control system 104.

FIG. 2 illustrates a block diagram 200 of the various subsystems in the system 100 for providing desired fan speed requests. In block 202, the engine controller 116 generates an engine temperature signal that corresponds to a temperature of the engine 108. The engine controller 116 transmits the engine temperature signal to the VSC 102. In one example, the engine controller 116 may be adapted to determine the measured temperature of the engine 108 by measuring the temperature of coolant in the first coolant loop 152. In another example, a plurality of temperature sensors (not shown) may be positioned proximate to or within the engine 108 to provide the temperature of the engine 108 to the engine controller 116. The VSC 102 determines a desired fan speed based on the engine temperature signal. The VSC 102 generates an engine fan speed signal that is based on the desired fan speed.

In block 204, the generator controller 122 generates a generator temperature signal that corresponds to a temperature of the starter-generator 112. The generator controller 122 transmits the generator temperature signal to the VSC 102. In one example, a plurality of temperature sensors (not shown) may be positioned proximate to or within the starter-generator 112 and measure the temperature of the starter-generator 112. The temperature sensors transmit the measured temperature to the generator controller 122. The generator controller 122 generates the starter-generator temperature signal in response to signals from the temperature sensors. The VSC 102 determines a desired fan speed based on the starter-generator temperature signal. The VSC 102 generates a starter-generator fan speed signal based on the desired fan speed. While FIGS. 1-2 illustrate a single starter-generator 112, additional starter-generators may be implemented in the system 100. The starter-generator controller 122 may be adapted to generate any number of starter-generator temperature signals that correspond to a multiple number of starter-generators.

In block 206, the generator controller 122 generates a power electronic circuit temperature signal that corresponds to a temperature of the power electronic circuitry used to drive the starter-generator 112. The generator controller 122 transmits the power electronics circuit temperature signal to the VSC 102. In one example, the generator controller 122 may be adapted to determine the measured temperature of the power circuitry by measuring the temperature of the coolant in the second coolant loop 156. In another example, a plurality of temperature sensors (not shown) may be positioned within the generator controller 122 to provide the temperature of the power circuitry to the generator controller 122. The VSC 102 determines a desired fan speed based on the power electronics temperature signal. The VSC 102 generates a power electronics circuit fan speed signal based on the desired fan speed.

In block 208, the DC/DC converter 114 generates a converter temperature signal that corresponds to a temperature of the DC/DC converter 114. The DC/DC converter 114 transmits the converter temperature signal to the VSC 102. In one example, the DC/DC converter 114 may be adapted to determine the operating temperature by measuring the temperature of the coolant in the second coolant loop 156. In another example, a plurality of temperature sensors (not shown) may be positioned proximate to or within the DC/DC converter 114 to measure the temperature. The VSC 102 determines a desired fan speed based on the converter temperature signal. The VSC 102 generates a converter fan speed signal based on the desired fan speed.

In block 210, the transmission controller 120 generates a transmission temperature signal that corresponds to a temperature of the transmission 110. The transmission controller 120 transmits the transmission temperature signal to the VSC 102. In one example, the transmission controller 120 is adapted to determine the measured temperature of the transmission 110 by measuring the temperature of coolant in the first coolant loop 152. In another example, a plurality of temperature sensors (not shown) may provide the temperature of the transmission 110 to the transmission controller 120. The VSC 102 determines a desired fan speed based on the transmission temperature signal. The VSC 102 generates a transmission fan speed signal based on the desired fan speed.

In block 211, the motor controller 135 generates a motor temperature signal that corresponds to a temperature of the motor 130. The motor controller 135 transmits the motor temperature signal to the VSC 102. In one example, the motor controller 135 is adapted to determine the measured temperature of the motor 130 by measuring the temperature in the second cooling loop 156. In another example, a plurality of temperature sensors (not shown) may provide the temperature of the motor 130 to the motor controller 135. The VSC 102 determines a desired fan speed based on the motor temperature signal. The VSC 102 generates a motor fan speed signal based on the desired speed.

In block 212, the VSC 102 determines the maximum fan speed from out of the engine cooling signal, the starter-generator cooling signal, the power electronic circuit cooling signal, the converter cooling signal, the transmission fan speed signal and the motor cooling signal. In block 214, the VSC 102 is further adapted to adjust the fan speed based on the maximum desired fan speed and to operate the cooling fan 160 at high, medium or low speeds.

FIG. 3 illustrates a flow chart 300 illustrating a strategy for controlling speed of the cooling fan 160 based on the subsystem fan speed signals. In step 302, the VSC 102 compares the subsystem fan speed signals against each other (e.g., the engine fan speed signal, the generator fan speed signal, the power electronic fan speed signal, the converter fan speed signal, the transmission fan speed signal, and the motor fan speed signal) to determine the maximum desired fan speed.

In step 304, the VSC 102 determines whether the maximum desired fan speed is above a first predetermined fan speed. If the maximum desired fan speed is above the first predetermined fan speed, the method 300 moves to step 306.

In step 306, the VSC 102 controls the cooling fan 160 to operate at a high speed. If the maximum desired fan speed is less than the first predetermined fan speed, the method 300 moves to step 308.

In step 308, the VSC 102 determines whether the maximum desired fan speed is less than a second predetermined fan speed. If the maximum desired fan speed is below the second predetermined fan speed, the method 300 moves to step 310.

In step 310, the VSC 102 controls the cooling fan 160 to operate at a low speed. If the maximum desired fan speed is greater than the second predetermined fan speed, the method 300 moves to step 312.

In step 312, the VSC 102 controls the cooling fan 160 to operate at a medium speed.

While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims. 

1. A system for controlling fan speed for a cooling fan in a vehicle; the system comprising: a plurality of vehicle subsystems configured to generate a plurality of subsystem temperature signals that are indicative of a measured temperature for each vehicle subsystem; and a vehicle controller configured to generate a desired fan speed signal for each vehicle subsystem in response to each subsystem temperature signal and to compare each desired fan speed signal to each other to determine a maximum desired fan speed signal, wherein the vehicle controller controls the fan to reach a speed that is equal to or greater than the maximum desired fan speed signal.
 2. The system of claim 1 wherein the vehicle controller is further adapted to compare the maximum desired fan speed signal to a first predetermined fan speed and to set the fan speed to a high speed if the maximum desired fan speed signal is greater than or equal to the first predetermined fan speed.
 3. The system of claim 2 wherein the vehicle controller is further adapted to compare the maximum desired fan speed signal to a second predetermined fan speed and to set the fan speed to a low speed if the maximum desired fan speed signal is less than the second predetermined fan speed.
 4. The system of claim 3 wherein the vehicle controller is further adapted to set the fan speed to a medium speed if the maximum desired fan speed signal is greater than the second predetermined fan speed and less than the first predetermined fan speed.
 5. The system of claim 1 wherein the vehicle subsystems comprise an engine controller and an engine, the engine controller being adapted to measure temperature of the engine and to generate an engine temperature signal, the vehicle controller is configured to determine an engine fan speed signal in response to the engine temperature signal.
 6. The system of claim 1 wherein the vehicle subsystems comprise a transmission controller and a transmission, the transmission controller being adapted to measure temperature of the transmission and to generate a transmission temperature signal, the vehicle controller is configured to determine a transmission fan speed signal in response to the transmission temperature signal.
 7. The system of claim 1 wherein the vehicle subsystems comprise a generator controller and a starter-generator, the generator controller being adapted to measure temperature of the starter-generator and to generate a starter-generator temperature signal, the vehicle controller is configured to determine a generator fan speed signal in response to the starter-generator temperature signal.
 8. The system of claim 7 wherein the generator controller comprises power electronic circuitry, the generator controller being adapted to measure temperature of the power electronic circuitry and to generate a power electronic circuit temperature signal, the vehicle controller is configured to determine a power electronic fan speed signal in response to the power electronic circuit temperature signal.
 9. The system of claim 1 wherein the vehicle subsystems comprise a DC/DC converter adapted to measure an internal operating temperature and to generate a converter temperature signal, the vehicle controller is configured to determine a converter fan speed signal in response to the converter temperature signal.
 10. The system of claim 1 wherein the vehicle subsystem comprises a motor controller and a motor, the motor controller being adapted to measure the temperature of the motor to generate a motor temperature signal, the vehicle controller is configured to determine a motor fan speed signal in response to the motor temperature signal.
 11. A method for controlling fan speed for a cooling fan in a vehicle, the method comprising the steps of: generating a plurality of subsystem temperature signals for a plurality of vehicle subsystems that are indicative of a measured temperature for each vehicle subsystem; generating a desired fan speed signal for each vehicle subsystem; comparing each desired fan speed signal to each other to determine a maximum desired fan speed signal; and controlling the fan such that the fan reaches a fan speed that is equal to or greater than the maximum desired fan speed signal.
 12. The method of claim 11 further comprising comparing the maximum desired fan speed to a first predetermined fan speed and controlling the fan speed to a high speed in response to determining that the maximum desired fan speed is greater than the first predetermined fan speed.
 13. The method of claim 12 further comprising comparing the maximum desired fan speed to a second predetermined fan speed and controlling the fan speed to a low speed in response to determining that the maximum desired fan speed is less than the second predetermined fan speed.
 14. The method of claim 13 wherein further comprising controlling the fan speed to a medium speed in response to the determining that the maximum desired fan speed is greater than the second predetermined fan speed and less than the first predetermined fan speed.
 15. The method of claim 11 wherein the vehicle subsystems comprise an engine controller and an engine, the engine controller being adapted to measure temperature of the engine and to generate an engine temperature signal, the vehicle controller is configured to determine an engine fan speed signal in response to the engine temperature signal.
 16. The method of claim 11 wherein the vehicle subsystems comprise a transmission controller and a transmission, the transmission controller being adapted to measure temperature of the transmission and to generate a transmission temperature signal, the vehicle controller is configured to determine a transmission fan speed signal in response to the transmission temperature signal.
 17. The method of claim 11 wherein the vehicle subsystems comprise a generator controller, a starter-generator, a motor controller and a motor, the generator controller is adapted to measure temperature of the starter-generator and to generate a starter-generator temperature signal, the motor controller is adapted to measure the temperature of the motor to generate a motor temperature signal, and the vehicle controller is configured to determine a generator fan speed signal in response to the starter-generator temperature signal and to determine a motor fan speed signal in response to the motor temperature signal.
 18. The method of claim 17 wherein the generator controller comprises power electronic circuitry, the generator controller being adapted to measure temperature of the power electronic circuitry and to generate a power electronic circuit temperature signal, the vehicle controller is configured to determine a power electronic fan speed signal in response to the power electronic circuit temperature signal.
 19. The method of claim 11 wherein the vehicle subsystems comprise a DC/DC converter adapted to measure an internal operating temperature and to generate a converter temperature signal, the vehicle controller is configured to determine a converter fan speed signal in response to the converter temperature signal.
 20. A system for cooling a control system in a vehicle, the system comprising: a cooling fan; a plurality of cooling loops; a plurality of vehicle subsystems configured to generate a plurality of subsystem temperature signals that are indicative of a measured temperature for each vehicle subsystem, the vehicle subsystems being positioned about the plurality of cooling loops; and a vehicle controller configured to: control the plurality of cooling loops to cool the vehicle subsystems in response to each subsystem temperature signal; generate a desired fan speed signal for each vehicle subsystem in response to each subsystem temperature signal; compare each desired fan speed signal to each other to determine a maximum desired fan speed signal; and control the fan such that the fan reaches a speed that is equal to or greater than the maximum desired fan speed signal. 